Hello Royell - I suppose the examination of the negative by the HSCA may have revealed something regarding the bench. I've read a little of their examination but don't recall if that was discussed.
-Side note: I want to make sure I have all the footage of the Nix film from Oliver Stone's JFK. I've only found one instance of it used in the film - about 16 frames during the courtroom assassination sequence. Anyone recall if there was more? - To my shock, it's just a video to 35mm transfer - shows all the tell-tale signs of a video source.